This invention relates in general to the manufacture and assembly of vehicle frame components and in particular to a method and apparatus for permanently joining two or more metallic vehicle frame components using magnetic impulse welding techniques.
Virtually all land vehicles in common use, such as automobiles and trucks, include a frame which serves as a platform upon which the remainder of the vehicle is built. Many vehicle frame structures are known in the art. Most of these known vehicle frame structures are formed from a number of individual metallic components which are permanently joined together. For example, a typical vehicle frame is composed of a pair of longitudinally extending side rails which are joined together by a plurality of transversely extending cross members. In shorter length vehicles, the side rails can be formed from a single piece of metal. In longer vehicles, however, each of the side rails is usually formed from two or more side rail sections which are permanently joined together. In either event, the side rails and cross members, once joined together, form a frame for supporting the remaining portions of the vehicle thereon. To facilitate the attachment of the other portions of the vehicle to the vehicle frame, a variety of brackets, hangers, cradles, and the like are often joined to the side rails and cross members at desired locations. It is common practice to also form these supporting hardware components from metallic materials, and further to permanently join them to the side rails and cross members at desired locations.
Conventional welding techniques have been commonly used to permanently join the various components of the vehicle frame together. As is well known, conventional welding techniques involve the application of heat to localized areas of two metallic members, which results in a coalescence of the two metallic members. Such welding may or may not be performed with the application of pressure, and may or may not include the use of a filler metal. Although conventional welding techniques have functioned satisfactorily in the past, there are some drawbacks to the use thereof in joining metallic vehicle frame components together. First, as noted above, conventional welding techniques involve the application of heat to localized areas of the two metallic frame members. This application of heat can cause undesirable distortions and weaknesses to be introduced into the metallic components. Second, while conventional welding techniques are well suited for joining components which are formed from similar metallic materials, it has been found to be somewhat more difficult to adapt them for use in joining components formed from dissimilar metallic materials. Third, conventional welding techniques are not easily adapted for joining components which have different gauge thicknesses. Inasmuch as the production of vehicle frames is usually an high volume, low margin process, it would be desirable to provide an improved method and apparatus for permanently joining two or more metallic vehicle frame components which avoids the drawbacks of conventional welding techniques.
This invention relates to a method and apparatus for permanently joining two or more metallic vehicle frame components using magnetic impulse welding techniques. In a first embodiment, the vehicle frame may include a pair of similar or dissimilar tubular side rail members in multiple sections joined together by a plurality of transversely extending closed (tubular or rectangular) or open (xe2x80x9cCxe2x80x9d of xe2x80x9cUxe2x80x9d shaped) cross members. A plurality of similar or dissimilar material brackets are joined to the side rails and/or cross members to facilitate the attachment of other portions of the vehicle to the vehicle frame. These components are joined via an overlap joint formed by the joining of two individual side rail sections, a cross member section and a side rail section, or a bracket and a side rail section or a cross member section. The first component and the second component, if tubular side rails, are sized so that they may be disposed telescopically with clearance. Similarly, the first component and second component, if a cross members/side rail, a bracket/cross member, or a bracket side/side rail, are sized and/or positioned so that some clearance exists between the components. An electromagnetic coil is provided for generating a magnetic field that causes the first component and the second component to move toward one another. Portions of the electromagnetic coil are disposed on either side of the side rail sections. A first end of the electromagnetic coil is connected through a switch to a first side of a capacitor, while a second end of the electromagnetic coil is connected directly to a second side of the capacitor. A source of electrical energy is provided for selectively charging the capacitor to store a quantity of electrical energy. By closing the switch, electrical energy is passed from the capacitor through the electromagnetic coil. Consequently, an intense electromagnetic field is generated about the first and second components. The presence of this electromagnetic field induces electrical currents in the first and second side rail sections. These electrical currents, in turn, create magnetic fields that draw the first and second components into contact with one another. When this occurs, the force generated by the magnetic fields cause the first and second components to move toward each other at great velocities. The high velocity of impact when the first and second components meet, and the large pressures produced on impact cause the first and second components to weld or molecularly bond. The first and second components, be they side rail sections, cross member sections, or brackets can include straight members, curved members, joint nodes, and member nodes. Some or all of these components can be formed by a hydroforming process, wherein high pressure fluid is introduced within a closed blank to expand portions thereof outwardly into conformance with an enclosing die. Initially, a closed tubular blank having a uniform circular cross sectional shape and formed from a metallic material is provided. The tubular blank may, if necessary, be pre-bent into a preform shape using a conventional tube bending apparatus. Next, the pre-bent blank is disposed within a hydroforming die, and highly pressurized fluid is introduced therein. The highly pressurized fluid causes portions of the pre-bent blank to expand outwardly into conformance with the hydroforming die. The final step is to join the formed structural members together to form the vehicle frame assembly. An electromagnetic coil can be used to cause the telescoping end portions of two structural members to move toward one another to generate a weld or molecularly bond the members together.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.